Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.41	11.446%	$223.3489	$223.35	$223.35	$223.30
Purchase #2	$112.44	5.114%	$118.1902	$118.19	$118.20	$118.20
Purchase #3	$166.76	11.384%	$185.744	$185.74	$185.75	$185.70
Purchase #4	$40.79	7.342%	$43.7848	$43.78	$43.80	$43.80
Purchase #5	$243.55	11.437%	$271.4048	$271.40	$271.40	$271.40
Purchase #6	$130.27	9.725%	$142.9388	$142.94	$142.95	$142.90
Purchase #7	$109.86	12.456%	$123.5442	$123.54	$123.55	$123.50
7 purchase totals =	$1,004.08		$1,108.9557	$1,108.94	$1,109.00	$1,108.80